Optical disk apparatus and track access control method utilizing positioned shift between scanning beams

Abstract

An optical disk apparatus includes first and second objective lenses, a carriage, a moving mechanism, a fixed optical system, a main control section, track access control circuits, a first positional shift correction circuit, a second positional shift correction circuit, first and second driving members, an arithmetic circuit, and a correction member. The first and second driving members slightly drive the first and second objective lenses in a track crossing direction in accordance with the first and second positional shift correction signals, respectively. The first and second positional shift correction circuits count first and second track position signals to output first and second positional error signals with respect to a target track, and output the first and second positional shift correction signals to the first and second driving members based on the first and second positional error signals and the first and second track position signals, respectively. The arithmetic circuit calculates a difference between the first and second positional error signals to output an inter-beam positional shift signal. The correction member corrects one of the first and second positional shift correction signals based on the inter-beam positional shift signal.

What is claimed is: 
     
       1. An optical disk apparatus comprising: first and second objective lenses respectively for outputting first and second light beams on the same track on an optical disk, the first and second beams separately recording, reproducing, and erasing information on the same track;   first and second driving means respectively for slightly driving said first and second objective lenses in a track crossing direction in accordance with a first and a second positional shift correction signals;   a carriage on which said first and second objective lenses are mounted;   a moving mechanism for moving said carriage between tracks;   a fixed optical system for emitting the first and second beams on said optical disk and detecting the beams reflected by said optical disk through said first and second objective lenses, and extracting first and second track position signals from the detected reflected beams of the first and second beams;   main control means for controlling an operation of said moving mechanism, and controlling an information recording/reproducing/erasing operation using said first and second objective lenses through said fixed optical system;   track access control means for controlling the movement of said carriage between the tracks based on the first and second track position signals from said fixed optical system;   first positional shift correction means for counting the first track position signal from said fixed optical system to output a first positional error signal with respect to a target track, and outputting the first positional shift correction signal to said first driving means based on the first positional error signal and the first track position signal;   second positional shift correction means for counting the second track position signal from said fixed optical system to output a second positional error signal with respect to said target track, and outputting the second positional shift correction signal to said second driving means based on the second positional error signal and the second track position signal;   arithmetic means for calculating a difference between the first and second positional error signals from said first and second positional shift correction means to output an inter-beam positional shift signal; and   correction means for correcting one of the first and second positional shift correction signals from said first and second positional shift correction means based on the inter-beam positional shift signal from said arithmetic means.   
     
     
       2. An apparatus according to claim 1, wherein said correction means comprises addition means for adding the inter-beam positional shift signal from said arithmetic means to one of the first and second positional shift correction signals from said first and second positional shift correction means. 
     
     
       3. An apparatus according to claim 1, wherein said first positional shift correction means comprises: first positional error signal generation means for counting the first track position signal from said fixed optical system to generate the first positional error signal with respect to the target track;   first reference speed signal generation means for generating a first reference speed signal for defining an inter-track moving speed of the first light beam based on the first positional error signal from said first positional error generation means;   first speed signal generation means for generating a first speed signal indicating a moving speed of the first light beam in the track crossing direction; and   first calculation means for calculating an error between the first reference speed signal from said first reference speed signal generation means and the first speed signal from said first speed signal generation means.   
     
     
       4. An apparatus according to claim 3, wherein said second positional shift correction means comprises: second positional error signal generation means for counting the second track position signal from said fixed optical system to generate the second positional error signal with respect to the target track;   second reference speed signal generation means for generating a second reference speed signal for defining an inter-track moving speed of the second light beam based on the second positional error signal from said second positional error generation means;   second speed signal generation means for generating a second speed signal indicating a moving speed of the second light beam in the track crossing direction; and   second calculation means for calculating an error between the second reference speed signal from said second reference speed signal generation means and the second speed signal from said second speed signal generation means.   
     
     
       5. An apparatus according to claim 3, wherein said second positional shift correction means comprises: second positional error signal generation means for counting the second track position signal from said fixed optical system to generate the second positional error signal with respect to the target track;   second speed signal generation means for generating a second speed signal indicating a moving speed of the second light beam in the track crossing direction; and   second calculation means for calculating an error between the first reference speed signal from said first reference speed signal generation means and the second speed signal from said second speed signal generation means.   
     
     
       6. An apparatus according to claim 1, wherein said moving mechanism is constituted by a carriage actuator, and said first and second driving means are constituted by lens actuators, respectively.